The basic features of surface finishing machines of the type that represent the preferred environment for the invention are shown in at least the following U.S. Patents, the entire contents of which are incorporated into reference, and a copy of which is enclosed as if fully set forth in the text of this document: U.S. Pat. No. 5,081,794 (Haney); U.S. Pat. No. 5,181,342 (Haney); U.S. Pat. No. 5,321,913 (Haney); U.S. Pat. No. 5,443,414 (Haney); U.S. Pat. No. 5,702,287 (Haney); U.S. Pat. No. 5,707,273 (Grivna); U.S. Pat. No. 4,473,500 (David); U.S. Pat. No. 4,837,984 (David); and U.S. Pat. No. 4,864,775 (David).
Such machines typically use a platen-mounted abrasive element that comprises an abrasive medium itself, e.g., sandpaper, emery cloth, or in general any thin paper-backed or fabric-backed sheet bearing a layer of finely sized abrasive particles, such as sand, ceramic, and the like. A resilient pad on the non-abrasive side of the abrasive material improves performance. Because of the forces created by very rapid motion required so the abrasive material does not leave scratches and other defects in the workpiece to be finished by the equipment, the supporting metal platen may itself be somewhat permanently mounted in the apparatus or not easily removable, depending on the configuration, so that it does not have a significant amount of mechanical play in its mounting subassembly. Thus, typically, replacement of the abrasive material requires removal and reconfiguration of any or all of the entire platen, the resilient material, and the abrasive material itself.
Thus, some means of removing the abrasive material (with or without the resilient pad accompanying it) must be provided so that the abrasive material may be changed as required. For example, as disclosed in FIGS. 5 and 6 and accompanying text of the Haney patents noted above, one approach is to secure an abrasive to the platen around a foam lying between the backside of the abrasive and the platen. Clips are used to secure the edges of the abrasive to the platen. Alternatively or additionally, the abrasive may be secured to the foam and platen by an adhesive. Haney defines ‘secured’ as meaning that the motion of the abrasive is completely dependent on the motion of the platen. Thus, when the platen moves the abrasive also moves. The foam is positioned between the platen and the abrasive to provide a soft touch to prevent the grit of the abrasive from scratching into a product too deeply. Without the foam, unwanted scratches would result from products that are not perfectly flat. Haney also discloses clips on both sides of the platen, and a spring-biased rod to operate the clips on the back side of the platen The rod includes a handle and arms. When the handle is pushed down, the rod rotates and the arms contact the clips and cause them to open. The rod can then be locked in place by a locking mechanism. The abrasive is then inserted between the clips and the platen. The clips close when the rod is released. The rod may be secured to a brace.